The Intelligent Network (IN) is able to generate and implement various new services in a fast, convenient, flexible, inexpensive and effective way. The objective of the IN is to serve all types of communication networks, including existing fixed communication networks such as a Public Switched Telephone Network (PSTN) and an Integrated Services Digital Network (ISDN) as well as mobile communication networks such as a Global System for Mobile Communication (GSM), a Universal Mobile Telecommunications System (UMTS), a north America Code Division Multiple Access (CDMA) system and a CDMA2000 system.
A characteristic of cellular communication systems is that, in principle, subscribers may use any cell of the system at any time, depending on their location when they use the cellular system. Hence, in contrast to fixed networks, the location of the subscriber cannot be deduced from the calling line.
However, cellular operators want to offer services where the tariffs are dependent on the subscriber's location. An example of such a service offering may be a “home service” (e.g. T-Mobile@home), where different tariffs are applied depending on whether customers access the cellular system through their “home cell(s)”, or through another cell of the cellular system. Furthermore, a service could be realized such that the subscriber may only use the network in his/her “home cell(s)” but not in any other cell of the network, the home cell(s) being defined as the cell(s) that provide coverage in a specific area, e.g. the subscriber's home.
Typically, the subscriber's current location in the network is known on an “area” granularity (e.g. Location Area in GSM telephony) when the mobile device is idle, and on a “serving cell” granularity when the mobile device is active. This applies to both the circuit switched and the packet switched domains of the cellular system.
In existing cellular systems, the service logic to implement the differentiation of tariff, or network access permission, based on the subscriber's serving cell resides in a “service layer” “above” the network layer. Typically, Intelligent Network (IN) technology and systems are employed. For GSM and UMTS systems as standardized by 3GPP, the Intelligent Network (IN) can request the subscriber's location from the network. This is done by the Intelligent Network (IN) system sending a location query to the HLR, which in turn requests the subscriber's current cell from the serving Mobile Switching Center/Visitor Location Register (MSC/VLR). Methods how the Intelligent Network (IN) determines the Home Location Register (HLR) from the subscriber's ID (e.g. the telephone number, International Mobile Subscriber Identification (IMSI) or another identity information) are state of the art today, and the subscriber's serving Mobile Switching Center/Visitor Location Register (MSC/VLR) is known to the Home Location Register (HLR) as described in the respective standards.
If, when receiving the location query from the Home Location Register (HLR), the Mobile Switching Center/Visitor Location Register (MSC/VLR) knows only the Location Area (LA) of the subscriber, it performs a “Paging” of the mobile device in all the cells of the LA so that the serving cell can be determined when the mobile device responds to the paging. This type of paging is not signaled on the mobile's Man Machine Interface (MMI), so that the subscribers are not alerted/disturbed by the paging process. Once the Mobile Switching Center/Visitor Location Register (MSC/VLR) has determined the subscriber's serving cell, it returns the cell ID to the Home Location Register (HLR) which in turn sends it back to the Intelligent Network (IN) for further service processing. This technique of the Intelligent Network (IN) retrieving the subscriber's serving cell ID is commonly known as “any-time interrogation” (ATI).
Operators are currently in the process of adding more access technologies to their cellular networks, specifically the e-UTRAN (also known as LTE) as specified by 3GPP. The resulting overall network is called the “Evolved Packet System” (EPS).
With the addition of further components to the cellular system beyond the GSM/GPRS/UMTS circuit and packet switched domains, the notion of the HLR was replaced by the concept of a “Home Subscriber Server” (HSS). The Home Subscriber Server (HSS) logically encompasses the legacy Home Location Register (HLR) and all other network related subscriber information, e.g. for the IMS. There is no standard, or even common idea, how the Home Subscriber Server (HSS) is physically implemented—in some cases, existing Home Location Registers (HLRs) are upgraded, in others a completely new node is deployed. In other cases, actual implementations physically separate the data storage (e.g. a common data base) of the HLR from the communication “frontend”, in which case the Home Location Register (HLR) frontend may be upgraded to include the Home Subscriber Server (HSS), or there may be a separate Home Subscriber Server (HSS) frontend.
In the Evolved Packet System (EPS), a new Mobility Management Entity (MME) performs equivalent mobility management functions to those of the MSC/Visitor Location Register (VLR) in the legacy circuit switched networks. However, the Mobility Management Entity (MME)
communicates with the Home Subscriber Server (HSS), not with the Home Location Register (HLR)
uses a different protocol towards the Home Subscriber Server (HSS) than legacy nodes towards the Home Location Register (HLR)
employs a different set of subscriber data.
This implies that enhancements are needed beyond the existing HLRs, or databases and their frontends, in order to perform the new functions via new protocols.